This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Damage to medial temporal lobe structures in monkeys impairs performance on a task of visual recognition memory, the Visual Preferential Looking Task (VPLT). The objective of this project is to identify the neuronal mechanisms that support memory performance on the VPLT in awake, behaving monkeys. In the past year, we have finished data collection and analyses which demonstrate that increased gamma-frequency (40-100 Hz) synchronization among hippocampal neurons is associated with enhanced recognition memory. We have shown, on a trial-by-trial basis, that Increased synchrony during encoding predicts successful subsequent recognition memory performance. These findings have been described in a manuscript, which is currently under review at Neuron. We have also completed analyses that demonstrate that individual hippocampal neurons modulate their firing rates based on stimulus novelty. Furthermore, the magnitude of this modulation is correlated with recognition memory performance. We are currently preparing a manuscript of these findings. Finally, we have recently collected data that demonstrate the existence of theta-band oscillations in the primate hippocampus.